1. Field of the Invention
The invention relates to a staple-driving gun, more particularly to a staple-driving gun with safety protection.
2. Description of the Related Art
Referring to FIG. 1, a conventional staple-driving gun is shown to include a gun body 1, a staple cartridge 3 and a piston unit 2.
The gun body 1 includes a handle 102, a staple-discharging member 103 formed with a staple-discharging hole 1032 that extends along an axis, and a hollow housing 101 connected fixedly to the handle 102 and having a first open end 1011, and a second open end 1012 opposite to the first open end 1011 along the axis and connected to the staple-discharging member 103. The housing 101 is configured with an inner surface that is divided into first and second air chambers 105, 106 by a partition 104 that is disposed fixedly in the housing 101 and that is formed with a valve hole 104′. The housing 101 is formed with an air inlet 109 in spatial communication with the first air chamber 105 for permitting compressed air to be fed into the first air chamber 105 therethrough.
The staple cartridge 3 is attached fixedly to the staple-discharging member 103, and is capable of receiving a row of staples (not shown) so as to feed the staples into the staple-discharging hole 1032 in the staple-discharging member 103 one at a time.
The piston unit 20 includes: a sleeve 201 disposed in the first air chamber 15, and having a coupling end portion 205 disposed movably in the first open end 1011 of the housing 101, and an enlarged valve end portion 207 disposed movably in the second air chamber 106 and having an outer diameter larger than a diameter of the valve hole 104′ in the partition 104; an operating member 206 connected fixedly to the coupling end portion 205 of the sleeve 201, disposed outwardly of the housing 101, and movable along the axis; and a piston rod 202 disposed movably in the sleeve 202 and having a diameter-increased first piston end 2021 that is in slidable and sealing contact with the sleeve 201, and a second piston end 2022 opposite to the first piston end 2021 along the axis, extending outwardly of the sleeve 201, and disposed movably and sealingly in the second air chamber 106. The second piston end 2022 of the piston rod 202 has a fixed staple-striking piece 204 that extends along the axis into the staple-discharging hole 1032 in the staple-discharging member 103.
The operating member 206 is operable so as to move the sleeve 201 from a standby position, where the valve end portion 207 of the sleeve 201 is in sealing contact with the partition 104 so as to seal the valve hole 104′ in the partition 104 such that flow of the compressed air from the first air chamber 105 into the second air chamber 106 through the valve hole 104′ in the partition 104 is prevented, as shown in FIG. 1, to a staple-discharging position, where the valve end portion 207 of the sleeve 201 is separated from the partition 104 so as to allow for flow of the compressed air from the first air chamber 105 into the second air chamber 106 through the valve hole 104′ in the partition 104 such that the compressed air flowing from the first air chamber 105 into the second air chamber 106 via the valve hole 104′ in the partition 104 urges the second piston end 2022 of the piston rod 202 to move toward the second open end 1012 of the housing 101, thereby discharging one of the staples in the staple-discharging hole 1032 in the staple-discharging member 103 in response to one strike of the staple-striking piece 204 thereon, as shown in FIG. 2.
However, if the operating member 206 is moved to the staple-discharging position due to an unintentional operation while the conventional staple-driving gun is in an unused state, i.e., the compressed air is not applied, as shown in FIG. 3, once the compressed air is applied to the conventional staple-driving gun, the undesired staple-discharging operation is performed, thereby resulting in danger during use.